The object of this project is twofold: (1) to learn about the natural history of chronic epileptogenic brain processes by comparative examination of chronological electroclinical features in idiopathic primary generalized (Senegalese baboon, Papio Papio) as against experimentally induced secondary generalized (Rhesus monkey, Senegalese baboon, and cats) epilepsies; and (2) to study the neurobiological factors underlying precipitation and inhibition of primary generalized as well as focal epileptic seizures. For this purpose (a) detailed examination of neural mechanisms underlying photogenic seizure susceptibility as well as primary generalized convulsive seizures in Senegalese baboon by serial lesioning and recording; (b) examination of the comparative electroclinical features of seizure development in non- epileptic rhesus monkeys and epileptic Senegalese baboons by daily amygdaloid stimulation; (c) daily electrical stimulation of frontal polar cortex in Both Senegalese baboon, Rhesus monkey and cats will be undertaken. In order to gain further insight into the underlying mechanisms of seizure generalization originating from either frontal polar cortex or amygdala a group of Senegalese baboons and Rhesus monkeys with midline parasaggital section of the forebrain commissures will be subjected to kindling study. Possible role played by cerebral motor cortex and cerebellum in amygdaloid or frontal seizure development will be examined in cats and sub-human primates by selective lesioning of the former and repetitive stimulation of the latter. Finally, attempts will be made to obtain insights into underlying neurochemical mechanism by examination of brain amino acids and the putative neurotransmitters acetylcholine and the monoamines. The latter investigation will involve the measurement of the levels of these compounds, examination of the levels of their synthesizing enzymes and assessment of the rate of turnover (synthesis and metabolism of the transmitter in question). Neurochemical manipulation by means of intracerebral administration of neurotoxic drugs will aid this aspect of our proposed study.